When Ethan Slater bounds onstage for the opening number of the new musical SpongeBob SquarePants at Broadway's Palace Theatre, he's clearly the title character even though he looks little like an animated rectangular sponge. Stylistic hints of his cartoon namesake -- a yellow shirt, a red tie, brown plaid pants, suspenders, and striped socks -- confirm his identity, yet he seems more like a person than a sea creature. And that's exactly what costume and set designer David Zinn was going for. The Tony winner wanted to convey the humanity of SpongeBob and his underwater pals while retaining the wackiness of the long-running Nickelodeon television series that inspired the show. So he opted to dress the characters in whimsical outfits rather than Times Square foam suits.

Featuring original songs written by an incredible roster of Grammy Award winners (Sara Bareilles, John Legend, Cyndi Lauper, Panic! At the Disco, even David Bowie), and a story that touches on environmental disaster, SpongeBob SquarePants was a novel design challenge for Zinn, who's been honing SpongeBob's look since the initial workshop almost five years ago. "That first workshop was literally about exploring if he isn't a yellow rectangle with pants on, then what is he?" Zinn says. "How far away from that can we get and still capture what people like about him and still make him recognizable? What captures his spirit?"

Since Slater, who's been with the project since the beginning, conveys so much of SpongeBob's goofy yet lovable soul, Zinn felt he could really play with the costume. "We didn't actually have to do a ton to make people identify him with the character and that was exciting," Zinn says. "That felt really freeing."

Likewise for SpongeBob's BFF Patrick the starfish (played by Danny Skinner), Zinn eschewed five arms in favor of a pink Hawaiian shirt that communicates his laid-back vibe. "We tried to make everything suit the particular craziness of the character," Zinn says. "Ethan and Danny have been with the show for so long, you learn what they can do that you don't have to do. You're allowing them to shine more. At this point I feel like there's nothing in the show that Ethan can't do. We have to put a pair of pants and a shirt on him, and then we get out of his way."

Wesley Taylor as Sheldon Plankton in 'SpongeBob SquarePants'

That said, some costume solutions were more complicated. For Sandy Cheeks (played by Lilli Cooper), a squirrel who sports an astronaut-like suit with a flower on her helmet, Zinn struggled to find the right combination of what would look familiar to fans but also be something a "groovy interesting girl" might wear. He settled on a cute white jumpsuit and pinned a blossom in her Afro. "People can tell it's her," Zinn says. "It makes Lilli feel like a cool person as opposed to a cartoon character."

Even for Sheldon Plankton, a tiny one-celled, one-eyed organism who's a villain of sorts, Zinn didn't want to go completely cartoonish. So actor Wesley Taylor wears a green suit, an eye patch, and slicked-back braids for a look Zinn describes as a combination of Dr. Evil, Rat Pack, and Steven Seagal. "We tried a bunch of things," Zinn says. "Does he need to wear a fake eye on top of his head? Does he need antennae? Does he need to be green? We tried all those things and it made him not human and that felt odd. Ultimately the stuff that was more costumey ended up feeling weird. The more he was just a guy wearing some clothes is when it started to be fun."

Since the random residents of the underwater town of Bikini Bottom didn't need to be recognizable, Zinn was able to go more outlandish with the ensemble. In the Nickelodeon series, the background characters are fish wearing polo shirts, but as Zinn notes, "a person wearing a polo shirt is not necessarily hilarious, so we had to make other rules of juxtaposition to create a similar texture. Big sculptural crazy colorful shapes is what became our vocabulary for the world surrounding our more human-centered principals."

Zinn's unique approach to SpongeBob's design has been championed since the outset. In fact when he went to Los Angeles to meet with the TV series' original animators and showrunners, they were clear that they only wanted to do a musical if they could find a fresh take. "Everybody at Nickelodeon has been very into us making our own thing," Zinn says. "We have to do that anyway because it's real people and not drawings."